Endophytic Fungal Community Composition Research Articles

Diversity and Composition of Endophytic Fungal Communities Associated with Cocoa (Theobroma cacao L.) Fruits in the Northern Ecuadorian Amazon

The study of microorganisms associated with tropical plant species, particularly fungi, has garnered significant interest due to their potential applications in biological control and the synthesis of pharmacologically active compounds. This research aimed to identify and characterize the endophytic fungal communities associated with cocoa (Theobroma cacao L.) fruits across three municipalities in the Orellana province, located within the Ecuadorian Amazon. Fungi were isolated directly from cocoa fruits and analyzed through comprehensive cultural, morphological, and molecular analyses. The diversity of fungal taxa was evaluated using metrics of relative abundance and species richness. A total of 464 fungal isolates were obtained, representing 56 distinct morphotypes and 14 genera within the phylum Ascomycota. The most abundant genera included Penicillium sp. (27.8%), Epicoccum sp. (20.5%), Lasiodiplodia sp. (10.1%), Trichoderma sp. (9.91%), and Fusarium sp. (9.70%). Notably, in the municipality of La Joya de los Sachas, a higher number of endophytic fungi was observed, encompassing 14 genera. This study provides critical insights into the diversity and distribution of fungal communities associated with cocoa fruits in the northern Ecuadorian Amazon. These findings have important implications for the management of cocoa diseases and the discovery of novel bioactive compounds. Future investigations should explore the functional roles of these fungi, particularly their potential as biocontrol agents or sources of novel pharmaceuticals. Furthermore, examining the effects of environmental variables and agricultural practices on cocoa fruit mycobiota may contribute to a deeper understanding of the ecological dynamics within this system.

Climate Change Drives Changes in the Size and Composition of Fungal Communities Along the Soil-Seedling Continuum of Schima superba.

Plant microbiomes have a major influence on forest structure and functions, as well as tree fitness and evolution. However, a comprehensive understanding of variations in fungi along the soil-plant continuum, particularly within tree seedlings, under global warming is lacking. Here, we investigated the dynamics of fungal communities across different compartments (including bulk soil and rhizosphere soil) and plant organs (including the endosphere of roots, stems and leaves) of Schima superba seedlings exposed to experimental warming and drought using AccuITS absolute quantitative sequencing. Our results revealed that warming and drought significantly reduced the number of specific fungal amplicon sequence variants (ASVs) in the bulk soil and rhizosphere soil, respectively. Variations in fungal communities were mainly explained by compartments and plant organs, with the composition of endophytic fungal communities within leaves (primarily attributed to species gain or loss) being most influenced by climate change. Moreover, warming significantly reduced the migration of Ascomycota, soil saprotrophs, wood saprotrophs and yeasts from the bulk soil to the rhizosphere soil but increased that of plant pathogens from the roots to the stems. Drought significantly decreased the absolute abundances of Chytridiomycota, Glomeromycota and Rozellomycota, as well as the migration of ectomycorrhizal fungi from the bulk soil to the rhizosphere soil but increased that of plant pathogens. Warming could indirectly reduce leaf area by increasing the diversity of leaf pathogens. These findings have potential implications for enhancing the resilience and functioning of natural forest ecosystems under climate change through the manipulation of plant microbiomes, as demonstrated in agroecosystems.

Sex-specific responses of Taxus mairei to UV-B radiation involved altering the interactions between the microbiota assembly and host secondary metabolism

BackgroundTo adapt to constantly changing environments, ancient gymnosperms have coevolved with diverse endophytic fungi that are essential for the fitness and adaptability of the plant host. However, the effect of sex on plant-endophyte interactions in response to environmental stressors remains unknown. RNA-seq integrated with ITS analysis was applied to reveal the potential mechanisms underlying the sex-specific responses of Taxus mairei to ultraviolet (UV)-B radiation.ResultsEnrichment analysis suggested that sex influenced the expression of several genes related to the oxidation–reduction system, which might play potential roles in sex-mediated responses to UV-B radiations. ITS-seq analysis clarified the effects of UV-B radiation and sex on the composition of endophytic fungal communities. Sex influenced various secondary metabolic pathways, thereby providing chemicals for T. mairei host to produce attractants and/or inhibitors to filter microbial taxa. Analysis of fungal biomarkers suggested that UV-B radiation reduced the effect of sex on fungal communities. Moreover, Guignardia isolate #1 was purified to investigate the role of endophytic fungi in sex-mediated responses to UV-B radiation. Inoculation with spores produced by isolate #1 significantly altered various oxidation–reduction systems of the host by regulating the expression of APX2, GST7 NCED1, ZE1, CS1, and CM1.ConclusionThese results revealed the roles of endophytic fungi in sex-mediated responses to UV-B radiation and provided novel insights into the sex-specific responses of Taxus trees to environmental stressors.3pQjBcj-im_YZSujzFCGpbVideo

Floral Volatile Organic Compounds Change the Composition and Function of the Endophytic Fungal Community in the Flowers of Osmanthus fragrans.

Endophytic fungi in flowers influence plant health and reproduction. However, whether floral volatile organic compounds (VOCs) affect the composition and function of the endophytic fungal community remains unclear. Here, gas chromatography-mass spectrometry (GC-MS) and high-throughput sequencing were used to explore the relationship between floral VOCs and the endophytic fungal community during different flower development stages in Osmanthus fragrans 'Rixiang Gui'. The results showed that the composition of the endophytic fungal community and floral VOCs shifted along with flowering development. The highest and lowest α diversity of the endophytic fungal community occurred in the flower fading stage and full blooming stage, respectively. The dominant fungi, including Dothideomycetes (class), Pleosporales (order), and Neocladophialophora, Alternaria, and Setophoma (genera), were enriched in the flower fading stage and decreased in the full blooming stage, demonstrating the enrichment of the Pathotroph, Saprotroph, and Pathotroph-Saprotroph functions in the flower fading stage and their depletion in the full blooming stage. However, the total VOC and terpene contents were highest in the full blooming stage and lowest in the flower fading stage, which was opposite to the α diversity of the endophytic fungal community and the dominant fungi during flowering development. Linalool, dihydro-β-ionone, and trans-linalool oxide(furan) were key factors affecting the endophytic fungal community composition. Furthermore, dihydro-β-ionone played an extremely important role in inhibiting endophytic fungi in the full blooming stage. Based on the above results, it is believed that VOCs, especially terpenes, changed the endophytic fungal community composition in the flowers of O. fragrans 'Rixiang Gui'. These findings improve the understanding of the interaction between endophytic fungi and VOCs in flowers and provide new insight into the mechanism of flower development.

Distribution patterns of endophytic fungi in different intertidal plant communities within a tropical mangrove forest in South China

Fungi play a crucial role in the growth of mangrove plants in various intertidal zones. However, our knowledge of the endophytic fungi in mangroves is limited. In this study, we analyzed the distribution patterns of endophytic fungi in true mangroves (TM), mangrove associates (MA), and other plants (OP) in a tropical mangrove forest. The results showed that Lulwoana, Fusarium, and Aspergillus were the predominant endophytic fungal taxa in TM, MA, and OP, respectively. Non-metric multidimensional scaling demonstrated significant differences in the endophytic fungal community structure among different intertidal plant communities, highlighting the plant-mediated selection of endophytic fungi. In addition, tides and plant species may affect endophytic fungal communities by altering soil properties. The colonization of arbuscular mycorrhizal fungi (AMF) and dark septate endophytes (DSE) was higher in MA, possibly because of variations in soil pH and available phosphorus content. Phylogenetic analyses indicated that family Diversisporaceae and Par1 (Paraglomeraceae) were exclusively found in the mangrove associates, whereas Glome4 (Glomeraceae) and Par2 (Paraglomeraceae) were observed only in the TM. These results support the high variation in AMF communities among the different intertidal plant communities. This study emphasizes the critical role of tides and plant species in shaping the composition of endophytic fungal communities, which has significant implications for the conservation and restoration of mangrove ecosystems.

Insights into diversity and L-asparaginase activity of fungal endophytes associated with medicinal plant Grewia hirsuta.

L-asparaginase is used as one of the prime chemotherapeutic agents to treat acute lymphoblastic leukemia. The present work aimed to study the endophytic fungal diversity of Grewia hirsuta and their ability to produce L-asparaginase. A total of 1575 culturable fungal endophytes belonging to four classes, Agaricomycetes, Dothideomycetes, Eurotiomycetes, and Sordariomycetes, were isolated. The isolates were grouped into twenty-one morphotypes based on their morphological characteristics. Representative species from each group were identified based on their microscopic characteristics and evaluation of the ITS and LSU rDNA sequences. Most of the fungal endophytes were recovered from the leaves compared to other plant parts. Diaporthe sp. was the predominant genus with a colonization frequency of 8.62%. Shannon-Wiener index for diversity ranged from 2.74 to 2.88. All the plant parts showed similar Simpson's index values, indicating a uniform species diversity. Among the sixty-three fungal endophytes screened, thirty-two were identified as L-asparaginase-producing isolates. The enzyme activities of fungal endophytes estimated by the nesslerization method were found to be in the range of 4.65-0.27 IU/mL with Fusarium foetens showing maximum enzyme activity of 4.65 IU/mL. This study for the first time advocates the production of L-asparaginase from Fusarium foetens along with the endophytic fungal community composition of Grewia hirsuta. The results indicate that the fungal endophyte Fusarium foetens isolated in the present study could be a potent source of L-asparaginase.

Diversity of endophytic fungal community in Huperzia serrata from different ecological areas and their correlation with Hup A content

BackgroundHuperzine A (Hup A) has attracted considerable attention as an effective therapeutic candidate drug used to treat Alzheimer’s disease. Whereas, the production of Hup A from wild plants faced a major challenge, which is the wild Huperzia Serrata harbor a low Hup A content, has a long-life cycle, and has a small yield. At present, several reports showed that Hup A is produced by various endophytic fungal strains isolated from H. serrata, thereby providing an alternative method to produce the compound and reduce the consumption of this rare and endangered plant. However, till now, very few comprehensive studies are available on the biological diversity and structural composition of endophytic fungi and the effects of endophytic fungi on the Hup A accumulation in H. serrata.ResultsIn this research, the composition and diversity of fungal communities in H. serrata were deciphered based on high-throughput sequencing technology of fungal internal transcribed spacer regions2 (ITS2). The correlation between endophytic fungal community and Hup A content was also investigated. Results revealed that the richness and the diversity of endophytic fungi in H. serrata was various according to different tissues and different ecological areas. The endophytic fungal communities of H. serrata exhibit species-specific, ecological-specific, and tissue-specific characteristics. There are 6 genera (Ascomycota_unclassified, Cyphellophora, Fungi_unclassified, Sporobolomyces, and Trichomeriaceae_unclassified) were significantly positively correlated with Hup A content in all two areas, whereas, there are 6 genera (Auricularia, Cladophialophora, Cryptococcus, Mortierella, and Mycena) were significantly negatively correlated with Hup A content of in all two areas.ConclusionsThis study indicated a different composition and diverse endophytic fungal communities in H. serrata from different organs and ecological areas. The current study will provide the realistic basis and theoretical significance for understanding the biological diversity and structural composition of endophytic fungal communities in H. serrata, as well as providing novel insights into the interaction between endophytic fungi and Hup A content.

Fungal Communities in the Native New Zealand Medicinal Plant Pseudowintera colorata (Horopito) Are Determined by Plant Organ Type and Host Maturity with Key Members Promoting Plant Growth.

The plant Pseudowintera colorata is well known for its antimicrobial and medicinal properties and is endemic to New Zealand. Using PCR-Denaturing gradient gel electrophoresis (DGGE), we investigated the factors influencing the composition of endophytic fungal communities in P. colorata from ten distinct sites across New Zealand. Our results showed that plant organs of P. colorata influenced the diversity and richness of endophytic fungi (PERMANOVA, p < 0.05). In addition, plant maturity and its interactions revealed that endophytic fungal communities formed discrete clusters in leaves, stems, and roots of mature and immature P. colorata plants (PERMANOVA; p = 0.002, p = 0.001 and p = 0.039, respectively). For identifying isolates with biocontrol potential, dual culture tests were set up against four different phytopathogenic fungi. Isolates with high activity (zone of inhibition > 10 mm) were sequenced and identified as Trichoderma harzianum, Pezicula neosporulosa, Fusarium tricinctum, Metarhizium sp., and Chaetomium sp. Applying selected endophytic fungi (n = 7) as soil drenchers significantly increased the growth of P. colorata seedlings and produced more internodes. Seedling shoots treated with Trichoderma sp. PRY2BA21 were 2.2 × longer (8.36 cm) than the untreated controls (3.72 cm). Our results elucidate the main plant factors influencing fungal community composition and demonstrate a role for endophytic fungi in P. colorata growth and further demonstrate that medicinal plants are a rich source of endophytes with potential as biocontrol agents.

Differences in the endophytic fungal community and effective ingredients in root of three Glycyrrhiza species in Xinjiang, China.

BackgroundEndophytic fungi influence the quality and quantity of the medicinal plant’s bioactive compounds through specific fungus-host interactions. Nevertheless, due to the paucity of information, the composition of endophytic fungal communities and the mechanism by which effective ingredients regulate endophytic fungal communities in roots remains unclear.MethodsIn this study, we collected root and soil samples (depth range: 0–20, 20–40, and 40–60 cm) of three Glycyrrhiza species (Glycyrrhiza uralensis, Glycyrrhiza inflata, and Glycyrrhiza glabra). Glycyrrhizic acid and liquiritin content were determined using high-performance liquid chromatography (HPLC), and total flavonoid content was determined using ultraviolet spectrophotometry. High-throughput sequencing technology was employed to explore the composition and diversity of the endophytic fungal community in different root segments of three Glycyrrhiza species. Furthermore, soil samples were subjected to physicochemical analyses.ResultsWe observed that the liquiritin content was not affected by the root depth (0–20 cm, 20–40 cm, and 40–60 cm). Still, it was significantly affected by the Glycyrrhiza species (Glycyrrhiza uralensis, Glycyrrhiza inflata, Glycyrrhiza glabra) (P < 0.05). In Glycyrrhiza root, a total of eight phyla and 140 genera were annotated so far, out of which Ascomycota and Basidiomycota phyla, and the Fusarium, Paraphoma, and Helminthosporium genera were found to be significantly dominant. Spearman correlation analysis revealed that liquiritin content was accountable for the differences in the diversity of the endophytic fungal community. Furthermore, distance-based redundancy analysis (db-RDA) showed that physicochemical properties of the soil (available potassium and ammonium nitrogen) and the root factors (liquiritin and water content) were the main contributing factors for the variations in the overall structure of the endophytic fungal community. Our results showed that the effective ingredients of Glycyrrhiza root and physicochemical properties of the soil regulated the endophytic fungal community composition and medicinal licorice diversity.

Molecular characterization of endophytic fungal communities associated with Vitis vinifera L. at Taif region of Saudi Arabia

Aim: The current study aimed to characterize the composition of endophytic fungal communities related to Taify grapevine leaves. Methodology: Taify grapevine leaves were collected from three different locations at Taif region. Total DNA was extracted and the endophytic fungal communities were investigated using next generation sequencing in a metagenomics approach. Results: The obtained data detected 26 fungal operational taxonomic units (OTUs) in all locations with variation in most taxa among three locations. The phylum Ascomycota dominated relative sequence abundance (90.83%), followed by Basidiomycota at 1.82%. Other unidentified fungi at phylum level dominated 7.35% abundance level. At genus level, Alternaria and Cladosporium genera were present at all locations, while Filobasidium and Didymella were detected in two locations. Most genera, Penicillium, Hanseniaspora, Fusarium, Chrysocorona and Quambalaria were detected in one location only. Interpretation: The present study confirmed the diversity of endophytic fungi in Taify grapevine, including pathogenic and non-pathogenic species. The detected species have potential to be used as biocontrol species against economically important pathogens such as Alternaria and Hanseniaspora. This will contribute to our understanding of grapevine-endophytic fungi interaction and their utilization to enhance grapevine production and quality. Key words: Endophytes, Fungi, Grapevine, Metagenomic, Next generation sequencing

Root Endophytic Fungal Community and Carbon and Nitrogen Stable Isotope Patterns Differ among Bletilla Species (Orchidaceae).

Orchids of the genus Bletilla are well-known ornamental plants and sources of traditional medicine in Asia that rely on the symbiotic relationship with root endophytic fungi throughout their whole life cycle. However, little is known about their fungal partners, infection pattern, and pathways of carbon gain. We investigated carbon and nitrogen stable isotope patterns in different organs of three Bletilla species, identified the root endophytic fungal community composition, and determined mycorrhizal colonization rates. The three Bletilla species were comprised by a polyphyletic group which belongs to different trophic modes, such as saprotroph, pathotroph, and symbiotroph; however, the dominant species and their abundances varied among Bletilla spp. Mycorrhizal infection rates also varied among Bletilla species, with B. striata (65% ± 25%) being significantly higher than those of B. formosana (35% ± 16%) and B. ochracea (22% ± 13%). Compared with surrounding autotrophic plants, all Bletilla spp. were significantly enriched in 13C with B. striata to a significantly higher level than other two Bletilla species. Among different organs, stems had higher δ13C values, while leaves and flowers had higher δ15N and total N content values across all three species. Our results indicate that the symbiotic relationship of Bletilla and its root endophytic fungi is not strictly specific. Although mycorrhizal infection rates were highly variable, the three Bletilla species had the same infection pattern with hyphae penetrating the cortex cell by the pathway cell. Different Bletilla species have different strategies for C allocation among plant organs. These findings provide new insights into the ecological adaptation of orchids and will contribute to Bletilla germplasm conservation and sustainable utilization.

Niche differentiation in the rhizosphere and endosphere fungal microbiome of wild Paris polyphylla Sm.

BackgroundThe plant microbiome is one of the key determinants of plant health and metabolite production. The plant microbiome affects the plant’s absorption of nutrient elements, improves plant tolerance to negative environmental factors, increases the accumulation of active components, and alters tissue texture. The microbial community is also important for the accumulation of secondary metabolites by plants. However, there are few studies on the niche differentiation of endophytic microorganisms of plants, especially at different elevations.MethodsWe investigated the effects of altitude on the community composition of endophytic fungal communities and the differentiation of endophytic microorganisms among different niches in Paris polyphylla Sm. The rhizosphere soil, roots, rhizomes and leaves of wild-type P. polyphylla Sm. at different altitudes were sampled, and the fungal communities of all samples were analyzed by internal transcribed spacer one amplification sequencing.ResultsThe results showed that in rhizosphere soil, the number of operational taxonomic units (OTUs) that could be classified or identified decreased significantly with increasing altitude, whereas in the endosphere of plants, the total number of OTUs was higher at intermediate altitudes than other altitudes. Furthermore, the structural variability in the rhizosphere fungal community was significantly lower than that in the endophytic communities. In addition, our results confirmed the presence of niche differentiation among members of the endophytic microbial community. Finally, we also determined that the predominant genus of mycobiota in the rhizome was Cadophora. This study provides insight into the relationships between the endosphere microbiome and plants and can guide the artificial cultivation of this plant.

Diversity and community of culturable endophytic fungi from stems and roots of desert halophytes in northwest China.

Halophytes have high species diversity and play important roles in ecosystems. However, endophytic fungi of halophytes in desert ecosystems have been less investigated. In this study, we examined endophytic fungi associated with the stem and root of ten halophytic species colonizing the Gurbantonggut desert. A total of 36 endophytic fungal taxa were obtained, dominated by Alternaria eichhorniae, Monosporascus ibericus, and Pezizomycotina sp.1. The colonization rate and species richness of endophytic fungi varied in the ten plant species, with higher rates in roots than in stems. The endophytic fungal community composition was significantly affected by plant identity and tissue type. Some endophytic fungi showed significant host and tissue preferences. This finding suggests that host identity and tissue type structure endophytic fungal community in a desert ecosystem.

Community Assembly of Endophytic Fungi in Ectomycorrhizae of Betulaceae Plants at a Regional Scale.

The interaction between aboveground and belowground biotic communities drives community assembly of plants and soil microbiota. As an important component of belowground microorganisms, root-associated fungi play pivotal roles in biodiversity maintenance and community assembly of host plants. The Betulaceae plants form ectomycorrhizae with soil fungi and widely distribute in various ecosystems. However, the community assembly of endophytic fungi in ectomycorrhizae is less investigated at a large spatial scale. Here, we examined the endophytic fungal communities in ectomycorrhizae of 22 species in four genera belonging to Betulaceae in Chinese forest ecosystems, using Illumina Miseq sequencing of internal transcribed spacer 2 amplicons. The relative contribution of host phylogeny, climate and soil (environmental filtering) and geographic distance (dispersal limitation) on endophytic fungal community was disentangled. In total, 2,106 endophytic fungal operational taxonomic units (OTUs) were obtained at a 97% sequence similarity level, dominated by Leotiomycetes, Agaricomycetes, Eurotiomycetes, and Sordariomycetes. The endophytic fungal OTU richness was significantly related with host phylogeny, geographic distance, soil and climate. The endophytic fungal community composition was significantly affected by host phylogeny (19.5% of variation explained in fungal community), geographic distance (11.2%), soil (6.1%), and climate (1.4%). This finding suggests that environmental filtering by plant and abiotic variables coupled with dispersal limitation linked to geographic distance determines endophytic fungal community assembly in ectomycorrhizae of Betulaceae plants, with host phylogeny being a stronger determinant than other predictor variables at the regional scale.

Secondary Metabolite Accumulation Associates with Ecological Succession of Endophytic Fungi in Cynomorium songaricum Rupr.

Cynomorium songaricum Rupr. is a rare root-parasitic plant distributed in the desert ecosystem. Little is known about the role of endophytes in accumulation of metabolites in C. songaricum. Here, the correlations between the seven active components (total sugars, flavonoids, protocatechuic acid, catechins, tannins, gallic acid, and ursolic acid) and the endophytic fungi of C. songaricum were investigated, and their causal relationships are discussed further. The results showed that the accumulation of these components and the assembly of endophytic fungi changed with different plant developmental stages. Diverse relationships including positive and negative correlation were found among chemicals and endophytic fungal operational taxonomic units based on correlation coefficient matrices, which demonstrated that the accumulation of secondary metabolites in C. songaricum is closely related to the endophytic fungal community composition. These results present new opportunities to deeply understand plant-fungal symbioses and secondary metabolite productions.

Endophytic fungi harbored in the root of Sophora tonkinensis Gapnep: Diversity and biocontrol potential against phytopathogens.

This work, for the first time, investigated the diversity of endophytic fungi harbored in the xylem and phloem of the root of Sophora tonkinensis Gapnep from three geographic localities with emphasis on the influence of the tissue type and geographic locality on endophytic fungal communities and their potential as biocontrol agents against phytopathogens of Panax notoginseng. A total of 655 fungal strains representing 47 taxa were isolated. Forty‐two taxa (89.4%) were identified but not five taxa (10.6%) according to morphology and molecular phylogenetics. Out of identifiable taxa, the majority of endophyte taxa were Ascomycota (76.6%), followed by Basidiomycota (8.5%) and Zygomycota (4.3%). The alpha‐diversity indices indicated that the species diversity of endophytic fungal community harbored in the root of S. tonkinensis was very high. The colonization and species diversity of endophytic fungal communities were significantly influenced by the geographic locality but not tissue type. The geographic locality and tissue type had great effects on the species composition of endophytic fungal communities. Forty‐seven respective strains were challenged by three fungal phytopathogens of P. notoginseng and six strains exhibited significant inhibitory activity. It was noteworthy that endophytic Rhexocercosporidium sp. and F. solani strongly inhibited pathogenic F. solani and other fungal phytopathogens of P. notoginseng.

Community structure of endophytic fungi of four mangrove species in Southern China

ABSTRACTMangrove forests play an important role in subtropical and tropical coastal ecosystems. Endophytic fungi are widely distributed in various ecosystems and have great contribution to global biodiversity. In order to better understand the effects of mangrove species and tissue types on endophytic fungal community, we investigated cultivable endophytic fungi in leaves and twigs of four mangroves Aegiceras corniculatum, Avicennia marina, Bruguiera gymnorrhiza, and Kandelia candel in Guangxi, China. The four tree species had similar overall colonisation rates of endophytic fungi (24–33%). The colonisation rates of endophytic fungi were higher in twigs (30–58%) than in leaves (6–25%) in the four plant species. A total of 36 endophytic fungal taxa were identified based on morphological characteristics and molecular data, including 35 Ascomycota and 1 Basidiomycota, dominated by Phomopsis, Phyllosticta, Xylaria, Leptosphaerulina, and Pestalotiopsis. The diversity of endophytic fungi was higher in twigs than in leaves in the four plant species. Some endophytic fungi showed host and tissue preference. The endophytic fungal community composition was different among four mangrove species and between leaf and twig tissues.

Concentration of Petroleum-Hydrocarbon Contamination Shapes Fungal Endophytic Community Structure in Plant Roots.

Plant-root inhabiting fungi are a universal phenomenon found in all ecosystems where plants are able to grow, even in harsh environments. Interactions between fungi and plant roots can vary widely from mutualism to parasitism depending on many parameters. The role of fungal endophytes in phytoremediation of polluted sites, and characterization of the endophytic diversity and community assemblages in contaminated areas remain largely unexplored. In this study, we investigated the composition of endophytic fungal communities in the roots of two plant species growing spontaneously in petroleum-contaminated sedimentation basins of a former petro-chemical plant. The three adjacent basins showed a highly heterogeneous pattern of pollutant concentrations. We combined a culture-based isolation approach with the pyrosequencing of fungal ITS ribosomal DNA. We selected two species, Eleocharis erythropoda Steud. and Populus balsamifera L., and sampled three individuals of each species from each of three adjacent basins, each with a different concentration of petroleum hydrocarbons. We found that contamination level significantly shaped endophytic fungal diversity and community composition in E. erythropoda, with only 9.9% of these fungal Operational Taxonomic Units (OTUs) retrieved in all three basins. However, fungal community structure associated with P. balsamifera remained unaffected by the contamination level with 28.2% of fungal OTUs shared among all three basins. This could be explained by the smaller differences of pollutant concentrations in the soil around our set of P. balsamifera sampless compared to that around our set of E. erythropoda samples. Our culture-based approach allowed isolation of 11 and 30 fungal endophytic species from surface-sterilized roots of E. erythropoda and P. balsamifera, respectively. These isolates were ribotyped using ITS, and all were found in pyrosequensing datasets. Our results demonstrate that extreme levels of pollution reduce fungal diversity and shape community composition in E. erythropoda. Our findings shed light on the effect of soil petroleum contamination on fungal endophytic communities and could help to develop strategies for improving phytoremediation using fungal endophytes.

The foliar endophytic fungal community composition in Cirsium arvense is affected by mycorrhizal colonization and soil nutrient content

Foliar fungal endophytes are ubiquitous, but understudied symbionts of most plant species; relatively little is known about the factors affecting their occurrence, diversity and abundance. We tested the effects of soil nutrient content and arbuscular mycorrhizal (AM) colonization on the occurrence of foliar endophytic fungi in Cirsium arvense in two field studies. In the first study, we assessed relationships between soil moisture, organic matter, carbon and nitrogen content and plant water, nitrogen and carbon content and AM colonization and the occurrence of foliar endophytic fungal species. In the second study, we manipulated soil nutrient content and AM colonization of potted seedlings and identified differences in endophytic fungal species composition of the leaves and stems. The results reveal that endophytes can occur either more or less frequently, depending on soil nutrient and plant water content and AM colonization. We propose that these patterns were the result of differences in fungal growth responses to nutrient availability in the leaves, which can be affected by resources obtained from the soil or symbiotic fungi in the roots.

Decline in diversity and abundance of endophytic fungi in twigs of Fagus sylvatica L. after experimental long-term exposure to sodium dodecylbenzene sulphonate (SDBS) aerosol.

Sodium dodecylbenzene sulphonate (SDBS) is an anionic synthetic detergent found in polluted sea aerosol and is known for its harmful effects on leaf surface ultrastructure on conifers and broadleaved trees. Four-year-old saplings of European beech were sprayed weekly for three consecutive growing seasons with either a 50 mg l(-1) solution of SDBS in deionized water or with pure deionized water (control). Two- to three- year-old twigs were collected from SDBS-treated and control plants during the growing season one year after the last treatment to isolate endophytic fungi. The frequency of colonization by endophytic fungi was significantly lower on SDBS-treated plants (63.8%) than on control plants (85.4%). Multiple colonization of twigs occurred more frequently and diversity of endophyte species was higher in control plants than in SDBS-treated plants. Thirty-six fungal species were isolated from 360 twigs. Cladosporium cladosporioides, Coryneum compactum, Phialocephala dimorphospora, and a species each of Mycosphaerella and Phomopsis were the most abundant endophytes with frequencies of colonization of more than 5%. The abundance of the Phomopsis species proved to be significantly reduced by the SDBS treatment. Within the limits of the indoor experimental conditions, the obtained results suggest that long-term exposure of aerial parts of beech to SDBS can affect the amount and composition of endophytic fungal communities of lignified twigs. Degradation of the leaf epicuticular wax layer and changes of the assimilation capacity and leaf water content (transpiration) of the crowns are presumed to be responsible for the reduction of endophytic fungi detected in twigs of SDBS-treated plants.